using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        List<Test> tests = new List<Test>();

        tests.Add(new Test { GroupId = 2, Name = "group 2 - one" });

        tests.Add(new Test { GroupId = 1, Name = "group 1 - one" });

        tests.Add(new Test { GroupId = 2, Name = "group 2 - two" });

        tests.Add(new Test { GroupId = 2, Name = "group 2 - three" });

        tests.Add(new Test { GroupId = 3, Name = "group 3 - one" });

        tests.Add(new Test { GroupId = 1, Name = "group 1 - two" });

        tests.Add(new Test { GroupId = 3, Name = "group 3 - two" });

        var info = tests.GroupBy(t => t.GroupId, t => t).Select(x => x.FirstOrDefault());

        foreach(var item in info) {

                Console.WriteLine(item.Name);

​

        }

    }

}

​

public class Test {

    public int GroupId { get; set; }

    public string Name { get; set; }

    public override string ToString()

    {

        return Name;

    }

}